(i) Technical Field
The present invention relates to a light-emitting device, a light-emitting device array, an optical recording head, an image forming apparatus, and a method of manufacturing the light-emitting device.
(ii) Related Art
A surface-emitting device array is used in a contact image sensor or a recording head of a printer. A typical surface-emitting device array is formed by integrating multiple light-emitting devices which are arranged on a single substrate in a linear form. As a representative example of a surface-emitting device, a light-emitting diode (LED), a light-emitting thyristor, and a laser diode are known. In the light-emitting diode, light radiation in an active region is isotropic, only a part of the radiated light is emitted from an uppermost layer, and light radiated toward a substrate is absorbed by the substrate.
Moreover, the light-emitting thyristor has a PNPN structure obtained by stacking compound semiconductor layers (GaAs, AlGaAs, or the like), and a gate voltage and/or a gate current is applied to a gate electrode, whereby light is emitted by the recombination of electrons and holes injected from an anode electrode and a cathode electrode. A self-scanning light-emitting device array has been put into practical use in which a light-emitting thyristor array having such a PNPN structure has a self-scanning function so that respective light-emitting thyristors are lit sequentially.